Many modern automobiles utilize a hybrid transmission system in which an internal combustion engine, electric machine(s), or combination of the two provides propulsion for the vehicle. In a typical hybrid transmission system, torque from the engine and electric machines is supplied to a plurality of gears to drive the wheels of the vehicle. Many typical hybrid transmissions provide only a single mode of operation. This single mode of operation presents overall system compromises. A decision must be made between a transmission that provides optimum torque during low speed operation or optimum efficiency for operation at highway speeds. Many typical hybrid transmissions are unable to provide both optimum low speed torque and highway speed efficiency. Typically, in an attempt to remedy this problem, large and powerful electric machines must be used. However, large and powerful electric machines are more expensive and take up more space within the hybrid transmission.
Alternatively, some hybrid transmissions provide multiple modes of operation whereby different transmission gear ratios may be achieved. However, typical prior art multi-mode hybrid transmissions include many gears and clutches and are very inefficient. For example, many prior art hybrid transmissions feature multiple planetary gear sets that must rotate at all times and lack availability of a selectable direct connection of one of the electric machines to the output shaft. This negatively impacts vehicle fuel economy. Moreover, many prior art hybrid transmissions often requiring numerous offset axes of rotation resulting in transmissions that are complex and large in size. This increases manufacturing costs and makes it difficult to package the hybrid transmission within the vehicle. Therefore, improvement in the art is desirable.